Optical technologies can be very powerful when it comes to detecting minute quantities of particulate in biological and pathogenic samples. More specifically, optical microscopy is also widely used in combination with fluorescence labeling for high resolution imaging of particulates (cells, microorganisms, etc.) in large laboratories and clinics. Fluorescent microscopes on the market are bulky and expensive due to their cumbersome assembly and high cost of optical elements forming them. Over the past few years, efforts have been made to find more compact and inexpensive imaging solutions to meet market needs by making use of low cost imaging technologies based on charge-coupled devices (CCD) or complementary metal-oxide-semiconductor (CMOS) sensor arrays.
Flow cytometry is a well-known laser based fluorescence technique that has experienced significant growth and innovation in recent years. This analytical laboratory technique can rapidly and very reliably measure different parameters on single cells and particles. Advances in the use of charge-coupled devices (CCD) have great potential in lowering prices by substituting expensive laser sources with much less expensive, up to two orders of magnitude, light-emitting diodes and sophisticated microscopes with simpler and more economic proximity detection schemes. These devices are known as image cytometers (I-CYTS) and can be easily operated through direct cell imaging on a computer screen. Unlike flow cytometers, I-CYTs do not work by illuminating the cells with a laser one by one but rather by imaging and analyzing thousands of cells in a single picture. For these reasons I-CYTs are gradually entering the market as they offer similar characteristics and benefits as conventional flow cytometers do but at a lower cost. U.S. Pat. Nos. 8,866,063 and 7,872,796 disclose microscope systems that use an image sensor, as is also the case for an image cytometer, that detect an image which is the replica of the sample in the space domain (known as the real or coordinate space). However, detecting the image in the space domain implies a tradeoff between spatial resolution, field of view (FOV) and depth of field (DOF). Resolution in optical microscope systems is limited by the diffraction limit (of the order of the wavelength of the light source, λ). In U.S. Pat. No. 7,872,796, a lenslet array is used to increase DOF of the device. However, FOV is still limited by the microscope objective in the system; therefore a λ/2 resolution can potentially be achieved with the device therein disclosed, but for reduced FOV. U.S. Pat. No. 8,866,063 describes a device with improved FOV by using an illumination source configured to scan the sample in at least two dimensions, capturing images in a plurality of scan locations. However, DOF is limited and the proposed solution to increase FOV implies lengthy computation to reconstruct the sample from the plurality of images captured; it also requires a cumbersome mechanical adaptation to provide the light source scanning.